Golang gorm 加入第二个 table 数据即将到来

Question

我是 Golang 中的新手，请假设我有 2 个如下所示的模型

type Jobs struct {
    JobID                  uint   `json: "jobId" gorm:"primary_key;auto_increment"`
    SourcePath             string `json: "sourcePath"`
    Priority               int64  `json: "priority"`
    InternalPriority       string `json: "internalPriority"`
    ExecutionEnvironmentID string `json: "executionEnvironmentID"`
}

type ExecutionEnvironment struct {
    ExecutionEnvironmentId string    `json: "executionEnvironmentID" gorm:"primary_key;auto_increment"`
    CloudProviderType      string    `json: "cloudProviderType"`
    InfrastructureType     string    `json: "infrastructureType"`
    CloudRegion            string    `json: "cloudRegion"`
    CreatedAt              time.Time `json: "createdAt"`
}

这是我的 Database connection & get jobs API 代码

package main

import (
    "encoding/json"
    "fmt"
    "net/http"
    "strconv"
    "time"

    "github.com/gorilla/mux"
    "github.com/jinzhu/gorm"
    _ "github.com/jinzhu/gorm/dialects/mysql"
)

type Jobs struct {
    JobID                  uint   `json: "jobId" gorm:"primary_key;auto_increment"`
    SourcePath             string `json: "sourcePath"`
    Priority               int64  `json: "priority"`
    InternalPriority       string `json: "internalPriority"`
    ExecutionEnvironmentID string `json: "executionEnvironmentID"`
}

type ExecutionEnvironment struct {
    ExecutionEnvironmentId string    `json: "executionEnvironmentID" gorm:"primary_key;auto_increment"`
    CloudProviderType      string    `json: "cloudProviderType"`
    InfrastructureType     string    `json: "infrastructureType"`
    CloudRegion            string    `json: "cloudRegion"`
    CreatedAt              time.Time `json: "createdAt"`
}

var db *gorm.DB

func initDB() {
    var err error
    dataSourceName := "root:@tcp(localhost:3306)/?parseTime=True"
    db, err = gorm.Open("mysql", dataSourceName)

    if err != nil {
        fmt.Println(err)
        panic("failed to connect database")
    }
    //db.Exec("CREATE DATABASE test")
    db.LogMode(true)
    db.Exec("USE test")
    db.AutoMigrate(&Jobs{}, &ExecutionEnvironment{})
}

func GetAllJobs(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Type", "application/json")
    fmt.Println("Executing Get All Jobs function")
    // var jobs []Jobs
    // db.Preload("jobs").Find(&jobs)
    // json.NewEncoder(w).Encode(jobs)
    var jobs []Jobs
    if err := db.Table("jobs").Select("*").Joins("JOIN execution_environments on execution_environments.execution_environment_id = jobs.execution_environment_id").Find(&jobs).Error; err != nil {
        fmt.Println(err)
    }
    json.NewEncoder(w).Encode(jobs)
}


func main() {
    // router
    router := mux.NewRouter()
    // Access URL
    router.HandleFunc("/GetAllJobs", GetAllJobs).Methods("GET")
    
    // Initialize db connection
    initDB()

    // config port
    fmt.Printf("Starting server at 8000 \n")
    http.ListenAndServe(":8000", router)
}

在 GetAllJobs 中，我尝试获取 jobs table 数据和 execution_environments table 数据。但是我的代码没有fetchexecution_environmentstable数据。请检查下面的示例 json：

[
    {
        "JobID": 4,
        "SourcePath": "test1",
        "Priority": 2,
        "InternalPriority": "test",
        "ExecutionEnvironmentID": "103"
    }
]

jobs table

execution_environments table

请帮我获取 json

中的 execution_environments table 数据

Answer 1

Job和ExecutionEnvironment之间的关系是belongs_to吗？

https://gorm.io/docs/belongs_to.html

如果是，只需将 ExecutionEnvironment 添加到您的作业结构中

type Jobs struct {
    JobID                  uint   `json: "jobId" gorm:"primary_key;auto_increment"`
    SourcePath             string `json: "sourcePath"`
    Priority               int64  `json: "priority"`
    InternalPriority       string `json: "internalPriority"`
    ExecutionEnvironmentID string `json: "executionEnvironmentID"`
    ExecutionEnvironment   ExecutionEnvironment `gorm:"foreignKey:ExecutionEnvironmentID"`
}

并且您应该能够获取 ExecutionEnvironment 数据

Answer 2

如果 Jobs 和 ExecutionEnvironment 之间的关系是一对一的，您的 Jobs 结构可能如下所示：

type Jobs struct {
    JobID                  uint   `json: "jobId" gorm:"primary_key;auto_increment"`
    SourcePath             string `json: "sourcePath"`
    Priority               int64  `json: "priority"`
    InternalPriority       string `json: "internalPriority"`
    ExecutionEnvironmentID string `json: "executionEnvironmentID"`
    ExecutionEnvironment   ExecutionEnvironment `gorm:"foreignKey:ExecutionEnvironmentID"`
}

接下来，要加载 Jobs 模型中的 ExecutionEnvironment 字段，您需要使用 Preload 函数。

如果您已经定义了两个表之间的关系（外键），您可以像这样获取数据：

var jobs []Jobs
if err := db.Preload("ExecutionEnvironment").Find(&jobs).Error; err != nil {
        fmt.Println(err)
}

如果没有，请尝试包含 Joins 函数：

var jobs []Jobs
if err := db.Preload("ExecutionEnvironment").Joins("JOIN execution_environments ee on ee.execution_environment_id = jobs.execution_environment_id").Find(&jobs).Error; err != nil {
        fmt.Println(err)
}

Golang gorm 加入第二个 table 数据即将到来

Golang gorm join 2nd table data's now coming

mysql

go

go-gorm

golang-migrate